This block of Columbus Avenue in North Beach is temporarily restored for traffic at the end of each work day.

With autumn just around the corner, tunnel pre-construction continues to move forward in SoMa, Union Square and North Beach. As tunneling contractor Barnard Impregilo Healy JV completes work along the alignment, new traffic configurations are being established at three construction sites.

At the construction site on 4th Street between Bryant and Harrison streets where tunneling will begin next year, the contractor expects to finish installing below-ground walls for the tunnel boring machine launch box on the west side of the block by the end of September. The construction zone will then move to the east side of the block, and a new traffic configuration will be established. We will provide additional details in advance of this change.

Farther north on 4th Street, the contractor completed installation of guide walls on the western portion of the block between Folsom and Howard streets. This weekthe contractor moved to the east side of the block and has begun demolishing utilities to prepare for guide wall installation. Two lanes remain open on the west side of the block. Guide walls are shallow, subsurface walls that help guide the equipment that will be used to construct the much deeper headwalls.

**UPDATE: The traffic configuration described here is now planned to begin the week of September 17.** In North Beach, the contractor plans to begin installing a sewer manhole on Columbus Avenue between Union and Powell streets next Thursday, September 13. To accommodate construction, the left lane for northbound traffic will be closed on this block during construction hours. Currently the right lane for northbound traffic is closed during construction hours on this block.

The contractor completed construction of these guide walls on the west side of 4th Street between Folsom and Howard streets. Work is now underway on the east side of this block.

Here’s what to expect in the next three weeks as tunnel pre-construction continues in SoMa, Union Square and North Beach:

Tunnel Launch Box (4th Street between Bryant and Harrison streets): The contractor will continue constructing below-ground walls around the perimeter of this major excavation site. Current work hours here are 5 a.m. to 1 a.m., Monday through Friday, and 6 a.m. to 4 p.m. on Saturday. At least two lanes of traffic on 4th Street will remain open at all times.

Yerba Buena/Moscone Station Headwalls (4th Street between Folsom and Howard streets): The tunneling contractor will install below-ground walls, called headwalls, at the site of the future Yerba Buena/Moscone Station. The walls will cross 4th Street at two points on this block. Current work hours at this site are 7 a.m. to 4 p.m., Monday through Friday. At least two lanes of traffic on 4th Street will remain open at all times.

Union Square Tunneling Pre-Construction (Stockton Street between Ellis and Geary streets and Ellis Street between Stockton and Powell streets): The contractor is performing utility demolition and ground stabilization work, called jet grouting. Installation of below-ground walls, called headwalls, will follow. Current construction hours at this site are Monday to Friday, 6 a.m. to 5 p.m. For more information about the traffic modifications now in effect in the Union Square area, check out this recent blog post.

North Beach Utility Relocation (Columbus Avenue between Union and Powell streets): The contractor will continue with utility relocation. Construction hours are Monday through Friday, 7 a.m. to 3:30 p.m. One lane of traffic will be closed at a time on one block of Union Street, Powell Street or Columbus Avenue during construction hours. For more information on construction in North Beach, check out this recent blog post.

A complete, current three-week construction schedule, including detailed, site-specific transit and traffic impacts, is available online for the tunnel contract. We also post construction, auto detour and Muni impact information on our projectGoogle Map.

We appreciate your continued patience while construction is in progress.